1. Field
The present invention relates to a fuel cell used as a power source for an electronic device, etc.
2. Description of the Related Art
Presently, a secondary battery, e.g., a lithium ion battery, is mainly used as a power source for electronic devices, such as portable notebook personal computers (notebook PCs), mobile devices, etc. In recent years, high-output miniature fuel cells that require no charging are expected as novel power sources, based on a demand for increased power consumption and prolonged operating time that are required by enhanced functions of the electronic devices. Among various types of fuel cells, a direct methanol fuel cell (DMFC) that uses a methanol solution as its fuel can handle the fuel more easily and has a simpler system than fuel cells that use hydrogen as their fuel. Accordingly, the DMFC is noticed as a promising power source for the electronic devices.
Normally, the DMFC comprises a fuel tank containing high-concentration methanol, a mixing tank in which the methanol in the fuel tank is diluted with water, a liquid pump for forcing the diluted methanol into an electromotive section, an air pump for feeding air into the electromotive section, etc. The electromotive section has an anode and a cathode and generates electric power through a chemical reaction by supplying air to the cathode side. As products of the reaction for the power generation, carbon dioxide and water are produced on the anode and cathode sides, respectively, of the electromotive section. The water as a reaction product is reduced to steam and discharged. The steam from the cathode side of the electromotive section is fed into a cooler through a cathode line, whereupon it is cooled and condensed into water. The resulting water is recovered and used to dilute the methanol. According to a fuel cell described in Jpn. Pat. Appln. KOKAI Publication No. 2004-95376, for example, an exhaust filter for removing toxic substances is provided on the downstream side of a cooler. In this arrangement, exhaust gas from the cathode side is cleared of toxic substances by the exhaust filter after passing through the cooler and then discharged to the outside.
In the fuel cell constructed in this manner, the cathode-side exhaust gas having passed through the cooler is further condensed into dew as it is cooled in the cathode line. Some of the water condensed in the cooler is blown up by the exhaust gas and discharged in splashes. Accordingly, the water flows through the cathode line into the exhaust filter, thereby wetting the filter. In consequence, there is a problem that the performance of the exhaust filter is lowered considerably.